Gas turbine combustion engines with can annular combustors require structures to transport the gasses coming from the combustors to respective circumferential portions of the first row of turbine blades, hereafter referred to simply as the first row of turbine blades. These structures must orient the flow of the gasses so that the flow contacts the first row of turbine blades at the proper angle, to produce optimal rotation of the turbine blades. Conventional structures include a transition, a vane, and seals. The transition transports the gasses to the proper axial location and directs the gasses into the vanes, which orient the gas flow circumferentially as required and deliver the gas flow to the first row turbine of blades. The seals are used in between the components to prevent cold air leakage into the hot gas path, and to smooth flow during the transition between the components.
Configurations of this nature reduce the amount of energy present in the gas flow as the flow travels toward the first row of turbine blades, and inherently require substantial cooling. Gas flow energy is lost through turbulence created in the flow as the flow transitions from one component to the next, and from cold air leakage into the hot gas path. Cold air leakage into the hot gas path through seals increases as seals wear due to vibration and ablation. Significant energy is also lost when the flow is redirected by the vanes. These configurations thus create inefficiencies in the flow which reduce the ability of the gas flow to impart rotation to the first row of turbine blades.
The cooled components are expensive and complicated to manufacture due to the cooling structures, exacting tolerance requirements, and unusual shapes. Layers of thermal insulation for such cooled components may wear and can be damaged. For example, vane surfaces and thermal insulation layers thereon are prone to foreign object damage due to their oblique orientation relative to the flow. Such damage may necessitate component repair or replacement, which creates costs in terms of materials, labor, and downtime. Thermal stresses also reduce the service life of the underlying materials. Further, the vanes and seals require a flow of cooling fluid. This requires energy and creates more opportunities for heat related component damage and associated costs.
Vanes are produced in segments and then assembled together to form a ring. This requires additional seals between the vane components, through which there may be more cold air leakage into the hot gas path. Further, these configurations usually require assembly of the components directly onto the engine in confined areas of the engine, which is time consuming and difficult.